1. Field of the Invention
This invention pertains to the field of cutting and/or gouging metal submerged in a non-volatile liquid, e.g. water. The largest field of use for the present invention is in the electric-arc cutting and gouging of metallic objects submerged under large bodies of water, such as rivers, lakes, oceans and the like. Typical submerged objects are sunken vessels, submerged portions of floating vessels such as ships, barges, and the like, fixed submerged structures such as bridge pilings, coffer dams, piers, offshore drilling platforms, pipelines and the like. The electrode of the present invention is suited for use with a torch such as described and claimed in U.S. Pat. No. 4,131,780. The torch of the '780 patent is in turn suited for the process described in co-pending application Ser. No. 687,931, filed May 19, 1976 now U.S. Pat. No. 4,273,982. In the aforementioned application a new process for Underwater Cutting and Gouging is disclosed. In the new process an arc is struck between an electrode and the workpiece after which high pressure fluid is forced against the molten metal thus clearing it from the cut or gouge. This new process is not dependent upon oxygen or chemical reaction as is required in the conventional Oxy-Arc Underwater Cutting Process.
2. Description of the Prior Art
Electrodes for use in conventional oxy-arc underwater cutting, and the prior art related to this field are adequately summarized in U.S. Pat. No. 3,835,288. The patentee discloses a hollow elongate metallic substrate over which is placed a precatalyzed thermosettable epoxy resin coating which serves to protect and crater the arc. In addition, the coating is waterproof and has electrically insulating properties. However, the tubular steel electrodes are made with bare ends so that an arc can be initiated between the electrode and the workpiece.
In U.S. Pat. No. 4,131,780 there is disclosed a copper coated graphite electrode having a waterproof coating for use with the claimed torch. The aforementioned co-pending application discloses the process and in detail sets forth that the graphite electrode covered with a thin coating of conductive metal is further covered with an insulating coating except for the tip. It was discovered that with this type of electrode if the tip were left uncovered, having neither a metallic coating nor the waterproof coating, water was absorbed into the graphite and on initiation of the arc the electrode could explode or performance thereof was less than desirable. Covering the tip prior to submerging of the electrode required scraping away of the waterproof coating in order to strike and maintain the arc.